KARACHI, Feb 11: The circuits of at least 25 Internet service providers have been down since Sunday evening because of some problem in the STM-1 Internet protocol backbone of the Pakistan Telecommunication Company.

Official sources told Dawn on Monday that the PTCL synchronous transfer module of the Internet protocol backbone had developed some fault on Sunday evening.

“The optical fibre running from Karachi to Fujairah, Dubai, Singapore, London and New York has become defective somewhere and it will take us some time to locate the fault and rectify it,” they explained.

As a result of this fault, the circuits of 25 Internet service providers as well as some banking and educational institutions had suffered, they admitted.

“There are two rates for optical fibre service. One is $6,000 per month for which no backup is provided by the PTCL.

The other is $9,900 per month for which backup is provided by the PTCL. Most Internet service providers have the optical fibre without backup facility.”

Some Internet service providers, however, switched over to satellite connection when STM-1 of the Internet protocol backbone was down, they said.